Hexagon KH-9: Meeting the challenge
The Hexagon KH-9 Reconnaissance Satellite is still considered one of the most complicated systems ever put into space.
Phil Pressel of Quartus Engineering wrote the book on the Hexagon Reconnaissance Satellite. Literally, he wrote the book — Meeting the Challenge: The Hexagon KH-9 Reconnaissance Satellite — considered the definitive account of an important chapter in US intelligence and aerospace history.
Developed in part by the Perkin-Elmer Corporation, where Pressel worked for 30 years, this satellite provided invaluable photographic intelligence to the US government, and even today, is considered one of the most complicated systems ever put into space. Hexagon operated between 1971 and 1986, and was the last film-based, orbiting photo-reconnaissance satellite. A guarded, government secret, the project was officially declassified in 2011.
Pressel's contribution to the development and operation of the Hexagon KH-9 was the design of the optical bar camera system that produced images at such a high-resolution level, "you could see a picnic blanket and count the number of people on it — under certain conditions you might see a ball tossed."
Watch Phil Pressel explain his work on Hexagon KH-9 at the National Museum of the US Airforce in 2016.
Even though the project ended 32 years ago, Pressel considers the Hexagon to still be one of the best satellites ever developed in the US, one reason being that its cameras used film. "It was not a zillion pixels as from a digital camera and it can be shown mathematically that film photography is really better than a zillion pixels," says Pressel.
The images released by the CIA/NRO after the mission was declassified showed the Hexagon cameras were able to get a resolution of two to three feet on the ground from about 100 miles away. "I can't tell you they were any better than that, because that's still classified," says Pressel with a smile, "but you can speculate that it could be much better under the right conditions."
In 1965, around the middle of the Cold War period, CIA Director John McCone wanted to develop a new satellite system to replace the then current NRO-issued Corona and Gambit reconnaissance satellites. The CIA envisioned a satellite with unparalleled technical requirements that could visually map most of the landmass of the earth, photograph selected areas of interest, and return the resulting film safely to Earth.
Meeting these requirements meant solving several problems including: avoiding blurred photos taken by a rotating camera with film moving at 200 inches per second at the focal plane, while riding in vehicle moving at over 17,000 miles per hour around a rotating Earth. The film needed to be controlled so it stayed perfectly synchronized with the rotating image and offered extremely high reliability over long periods of time.
This National Reconnaissance Office-released graphic details the huge Hexagon spy satellite, A Cold War-era surveillance craft that flew reconnaissance missions from 1971 to 1986. The bus-size satellites weighed 30,000 lbs and were 60 ft long. Credit: NRO
The team at Perkin-Elmer had to design brushless motors (non-existent at the time) that wouldn't create debris or electrical noise. They would also designed optical encoders to control motor speeds, commutation, and perform several analytical functions.
All systems had to work perfectly at all times, as the satellite was autonomous — there would be no technicians aboard to fix any issues.
"When we first saw the requirements the CIA wanted, we said this is crazy, we'll never get this to work," says Pressel. The CIA envisioned a satellite that was 60-foot long, weighed 30,000 pounds, and took clear images with a resolution of 2 to 3 feet. "The precision and complexity blew our minds, but we made it work."
Several companies would take part in the project — Eastman Kodak made the film; the cameras and optics systems were made at Perkin-Elmer; the McDonnell-Douglas company made the re-entry vehicles; and Lockheed Corporation integrated and built the satellite.
Pressel adds that in those days, engineers and technicians didn't have significant computer capabilities. "We had early versions of a program called NASTRAN. We did all of this incredibly complicated work with slide rules and eventually calculators. We used old technology, and it worked!"
In a presentation at SPIE Optics and Photonics 2018, he explained how the optical system worked in perfect synchronization with the fast-moving film (linearly and in rotation).
Each Hexagon satellite carried two f/3 60-inch, focal length folded Wright stereo cameras — Pressel headed the mechanical design team for the cameras. One camera faced forward and the other faced aft, permitting pictures to be taken in stereo. The cameras rotated in opposite directions from each other for momentum compensation. If they rotated in the same direction, the vehicle would have wobbled significantly.
At the beginning of the program, a mission lasted about 52 days and each of the two cameras carried about 20 miles of film that was 6.6 inches wide and about 2000ths of an inch thick. As the technology kept improving, the film got thinner — and eventually used both black-and-white and color film interspersed throughout its length. Later missions would last for months, with the longest lasting 285 days. Most of those later missions carried about 30 miles of film in each camera.
Other mechanisms developed for the Hexagon's camera system included "the Looper," a film storage device that drew the film from the supply reels into its entrance while simultaneously feeding film to the platen for exposure thus allowing up to 120 feet of film to be instantly available for photography upon command. A mechanism known as "the Twister" was a self-aligning, passive device that allowed the film to be rotated in synchronization with the rotating optical bar during photography while the film was also traveling linearly.
The Hexagon cameras not only took images of military assets, but also took economic intelligence. "We could see if they had a good or bad crop season; if there were floods or damaged land areas," says Pressel. "That told us a lot about their economic status."
"We were never allowed to talk about anything, not even at home," says Pressel. Not until declassification in 2011, would any family members of those involved with the project learn what really went on "at the office."
"There were several taboo words, such as ‘optical bar,' and ‘Hexagon.' We used abbreviations and talked in code."
This code included acronyms such as "LO "for looper, PL for platen, "OB" for optical bar, and "SU" for supply unit. The biggest taboo word was "film," as it would automatically denote "camera," which would give away the whole project. The code word "material" was used instead.
If speaking on the phone to anyone from Lockheed or other companies involved in the project, using code was strictly enforced. If either party in a conversation used a taboo word, the person on the other end would immediately hang up.
Tight security was also maintained when traveling. "We couldn't carry any identification or documents that tied us to Perkin-Elmer, such as a badge, not even a pencil with the company name," says Pressel. "When we got to our destination, for example at Lockheed, we signed in as ‘self,' not as representing any company. In some cases, we were told not to stay at certain hotels, because the rooms might be bugged." These measures weren't necessary for personal travel, such as family vacations, but anyone working on the Hexagon mission was not allowed to travel to any communist countries or what the CIA deemed "denied territories."
When the Hexagon's film canisters were full, they were released one at a time from the orbiting vehicle. At a certain altitude, a parachute deployed, and the floating unit was caught by a Lockheed C-130 Hercules military aircraft. The film was then brought to Hawaii and shipped to the CIA for analysis. But one day in 1972, the parachute didn't deploy, the plane couldn't catch it, so the vehicle hit the water with a force of about 2000 Gs and sank in over 16,000 feet of water in the middle of the Pacific.
"The CIA thought there was a possibility that in the middle of these huge, tightly wound film reels, there might be some valuable pictures," Pressel explains. "So they wanted to retrieve it. There were often Russian trawlers in the area and they certainly didn't want the Russians to go down and go after it. "Per CIA request, Perkin-Elmer designed a huge claw to grab the sunken canister. The CIA also requested the Navy aid in the recovery with the Trieste, a bathysphere capable of submerging to much greater depths. Along with bad weather and several practice runs, it took months to finally bring up the container.
"The CIA didn't want the sailors aboard to know what they had, so they said put a black tarpaulin over the whole thing before it comes up, so they don't find out," says Pressel.
Unfortunately, the canister had been destroyed on impact, and the film had disintegrated — broken up in small pieces. "They never got any data from it, but the CIA was still happy we went after it," says Pressel. "And those sailors were very unhappy that they never found out what the mystery was."
Before writing Meeting the Challenge, Pressel wrote another book, They Are Still Alive, which chronicles his family's escape from the Holocaust during World War II. Born in Antwerp, Belgium, Pressel was almost 4 years old when Germany invaded Belgium in 1940. The family would spend the next five years hiding in various places in France, always ready to move again if they were exposed as Jews. At one point, Pressel was separated from his parents and sheltered for several months with a Catholic family. "I didn't even know I was Jewish at the time," Pressel writes in the book. "My parents never told me — for my own safety."
After the war, Pressel's father, who was fluent in eight languages, was hired as a translator for the United Nations, so the family relocated to New York City in 1946. "The rest is history," says Pressel in the matter-of-fact manner of an engineer. "I went to school, learned English, graduated college, and became a mechanical engineer."
Pressel says he wanted to write the book for his children and grandchildren, so they would know about their heritage and learn how some family members survived the war, but many others didn't. When he finished that project, he realized he enjoyed the process of writing and wanted to tell the story of the Hexagon KH-9 Reconnaissance Satellite — although at the time, the project was still classified. He says writing the book was a "labor of love" to honor all those who had worked so hard to make the project successful.
"I contacted the CIA, told them what I wanted to do, and they invited me down to talk," says Pressel. "They finally gave me written permission to write a book about the Hexagon, with the proviso that I couldn't tell anyone about it until the project was de-classified."The CIA also required the book be written "in a secret environment," something Pressel had no problem with as he already had many years of practice with keeping secrets. The manuscript was written on a dedicated laptop with an external hard drive, so it was never connected to the Internet. Every day, after he was finished writing, the hard drive was placed in a safe that was bolted to the floor of his bedroom closet. "Plus," adds Pressel, "I wrote the whole thing encrypted."
The CIA seemed happy with the safety measures, and when the Hexagon project was de-classified in 2011, Pressel, who was still working on the book, was given the go-ahead to publish.
Soon after the book came out, Pressel was contacted by people who had worked on the project, thanking him for telling their story. Some technicians who had worked on one part of the satellite were thrilled to learn the details of the rest of the satellite's many parts.
"I was also contacted from a gentleman who worked at Vandenberg as a technician on the rockets that sent up the Hexagon satellites," says Pressel laughing. "He said he read the book and finally found out after all these years what the payload was!"
MORE STORIES TO TELL
Now 81 years old, Pressel has many stories to tell about his more than 50 years as a mechanical engineer working mostly on highly classified programs, and shares these at conferences around the country. The smile on his face as he discusses the intricacies of the Hexagon KH-9 shows his pride in a project he feels helped save lives.
"The intelligence that we gathered, enabled President Nixon to sign the SALT-1 Treaty, a strategic arms-limitations treaty, because Hexagon photos verified the Soviet Union's claims about its weapons stockpiles," says Pressel. "In the 1980s when President Reagan said, ‘Trust, but verify,' we had the cameras that were verifying what everybody else was doing."
Hexagon's main purpose was, in a way, to prevent wars, as it was designed to spot missile silos and troop movements. There were 19 successful Hexagon launches — the 20th flight blew up on the pad in April 1986. The KH-9 series was later replaced with the KH-11, which used digital photography technology.
"I never wanted to work on an offensive weapon system that would kill people, because I was a survivor of war," says Pressel. "I was bombed, I was shot at, and I was chased; I was secluded from my parents for a long time. I'm still traumatized by it, so, no - I don't like war, but I support our nation and our security, so I worked on intelligence issues rather than weapons. I think the Hexagon helped prevent World War III."
During his long career at Perkin-Elmer, Pressel worked on several projects, such as the Hubble Telescope's fine-guidance system, but about 90% of his work was classified for the CIA, "which I still can't talk about," he says with a smile. So as more projects are declassified, who knows what new stories Phil Pressel will have to add to his presentations?
San Diego Navy Yard, California
Eiffel Tower in Paris, France
The Vatican in Rome, Italy
Related SPIE content:
Read about the history of the formerly top-secret KH-9 Hexagon spy satellite on the SPIE Digital Library.
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